chore(design): stats-overhaul 设计 WIP — CONTRACT + ui_kits 统计页规格

stats-overhaul 的设计稿(CONTRACT.md + mobile/tablet/desktop ui_kits)。

注:这批 ui_kits 描述的是统计页「上聚合·下分设备」原方案;统计页后续已
重设计为「月/周/日 周期卡 + 设备下拉 + 两周折线」(见 client/lib/screens/
stats_page.dart)。设计稿与新页布局有出入,待更新到新布局(单列 TODO 跟踪)。

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

design/ui_kits/desktop/dparts.jsx

@@ -70,6 +70,7 @@ const DSTRINGS = {
   search:{zh:'搜索国家 / 城市',en:'Search country / city'},
   trafficMonth:{zh:'本月流量',en:'Traffic'}, avgPing:{zh:'平均延迟',en:'Avg ping'}, durMonth:{zh:'本月时长',en:'Time'},
   weekTraffic:{zh:'本周流量 (GB)',en:'This week (GB)'},
+  byDevice:{zh:'设备明细',en:'By device'}, noDeviceUsage:{zh:'暂无设备用量',en:'No device usage yet'},
   autostart:{zh:'开机自启动',en:'Launch at login'}, autostartSub:{zh:'登录系统时自动启动穿山甲',en:'Start Pangolin when you log in'},
   smartRoute:{zh:'智能分流',en:'Smart routing'}, smartRouteSub:{zh:'海外应用加速,本地直连',en:'Accelerate overseas apps, keep local direct'},
   killSwitch:{zh:'Kill Switch',en:'Kill Switch'}, killSwitchSub:{zh:'断线时阻断网络,防止 IP 泄露',en:'Block all traffic if connection drops'},